Amphibious fishes are a facultative air-breathing fishes defined by their innate ability to spend part of their life out of water. These fishes not only remain on land but also move across the ground in various ways. A wide diversity of fish species exhibits amphibious behaviors for multiple reasons, including specialized feeding strategies, reproductive activities, predator avoidance, competition reduction in densely populated habitats, or as a response to environmental stressors such as elevated water temperatures or significant decreases in water levels. However, our current understanding of the factors driving terrestrial movement in fishes does not clearly elucidate the internal mechanisms responsible for initiating this behavior.
Russian and Vietnamese scientists conducted an experimental study aimed at investigating the endocrinological and biochemical changes in the blood of climbing perch Anabas testudineus associated with terrestrial movements. A specialized testing apparatus was employed to evaluate differences in biochemical parameters between fish held in aquatic conditions and those during terrestrial movements induced by a rapid decrease in water levels. The concentrations of eight biochemical parameters were measured using ELISA and biochemistry analyzer in individual blood serum samples.
The study showed that climbing perch primarily undertakes terrestrial movements in response to significant environmental stressors, such as the rapid decline in water levels observed in this study. Both primary and secondary stress responses were identified in climbing perch, characterized by elevated levels of cortisol and glucose in the blood serum of individuals exposed to terrestrial conditions, compared to fish maintained in aquatic environments. Based on these findings, it was suggested that terrestrial movements in climbing perch are often forced and carry a high risk of mortality, as their on-land navigation and ability to locate new water bodies have not been conclusively demonstrated.
SRS of IEE RAS, Efim Pavlov reported: “The changes in lipid and enzyme profiles indicate energy mobilization in climbing perch during terrestrial movements. This process imposes a significant energetic cost on the fish compared to their regular swimming.”
The present study offers the first detailed insights into the biochemical mechanisms underlying the adaptation of amphibious fish to terrestrial locomotion. Understanding the adaptive potential of these fish is crucial for informing their conservation prospects amid increasing anthropogenic pressures on freshwater environments. Terrestrial movements are a key aspect of the life cycle of amphibious fish, contributing to their survival and supporting the maintenance of population diversity under the influence of global warming.
Article was published in Stresses journal: Stress and Energy Mobilization Responses of Climbing Perch Anabas testudineus During Terrestrial Locomotion, Efim D. Pavlov, Tran Duc Dien and Ekaterina V. Ganzha, Stresses 2025, 5(3), 45.